The innate immune response is a primary defense mechanism to combat microbial infection. In addition to providing necessary cues for the initiation of an adaptive immune response, activation of the innate signaling pathways triggers immediate and localized defensive activities. An important component of this response is the induction of proteins that have direct antiviral activities. Since viruses have developed molecular strategies to circumvent these activities, these restriction factor proteins impose strong constraints on viral evolution. Elucidate a global understanding of the molecular circuits that underlie these innate activities would provide opportunities for the development of novel antiviral therapeutics targeting this critical viral-host interface. Dengue (DENV) and West Nile (WNV) virus are members of the Flaviviridae family of positive strand RNA viruses. These viruses can activate Pattern Recognition Receptors, such as TLR3, TLR7, or RIG-I, which specifically respond to molecular signatures harbored by these viruses. Additionally, both dengue and West Nile virus harbor proteins that function to inhibit downstream type-1 interferon signaling (i.e. NS4B). This strongly suggests that activation of type-1 interferon induces the expression of target genes that directly impede the viruses' ability to effectively replicate. The goal of the proposal is to integrate two systems-level analytical technique, genome-wide mammalian genetic analysis and affinity purification mass spectrometry, to establish a global understanding of the host-pathogen molecular networks that underlie both innate immune-mediated restriction of viral replication, and viral countermeasures to these activities. A comprehensive, systems-level, analysis of these virus-host interactions will provide significant new molecular insight into the network infrastructure is regulated by the innate immune response to RNA virus infection.